Nuclear effects in coherent photoproduction of heavy quarkonia

TL;DR

This paper investigates the coherent photoproduction of heavy quarkonia on nuclear targets using the QCD color dipole formalism, accounting for various nuclear effects and comparing with experimental data, providing predictions for future measurements.

Contribution

It introduces a comprehensive QCD color dipole model that includes impact parameter correlations, multiple shadowing effects, and quantum coherence considerations, advancing the understanding of quarkonium production in nuclear collisions.

Findings

Good agreement with ALICE data on charmonium production

Predictions for $ ext{ψ'}$(2S) and Υ states for future tests

Analysis of quantum coherence effects in nuclear shadowing

Abstract

Coherent photoproduction of heavy quarkonia on nuclear targets is studied within the QCD color dipole formalism including several main phenomena: i) The correlation between impact parameter of a collision $\vec b$ and dipole orientation $\vec r$; ii) The higher-twist nuclear shadowing related to the $\bar QQ$ Fock state of the photon; iii) The leading-twist gluon shadowing corresponding to higher Fock components of the photon containing gluons; iv) Reduced effects of quantum coherence in a popular Balitsky-Kovchegov equation compared to calculations, which are frequently presented in the literature. Our calculations of differential cross sections are in good agreement with recent ALICE data on charmonium production in ultra-peripheral nuclear collisions. We present also predictions for coherent photoproduction of other quarkonium states ($\psi^{\,\prime}$(2S), $\Upsilon$(1S) and $\Upsilon^{\,\prime}$(2S)) that can be verified by future measurements at the LHC.